Multi-RIS Aided VLC Physical Layer Security for 6G Wireless Networks

Recent studies highlighted the advantages of Visible Light Communication (VLC) over radio technology for future 6G networks. Thanks to the use of Reflective Intelligent Surfaces (RISs), researchers showed that is possible to guarantee communication secrecy in a VLC network where the adversary location is unknown. However, the problem of authenticating the transmitter with a low-complexity physical layer solution while guaranteeing communication secrecy is still open. This paper proposes a novel multi-RIS architecture to guarantee source authentication, communication secrecy, and integrity in a VLC scenario. We leverage the intuition that a signal transmitted by users located in different positions will undergo a different propagation path to discriminate between the legitimate intended transmitter and an attacker. To increase the channel's variability and reduce the chances that an adversary might be able to replicate it, we leverage the reconfiguration capabilities of RIS. We derive a statistical characterization of the non-line-of-sight VLC channel, representing the light reflected by RIS elements. Via numerical simulations, we show that the channel variability combined with the configurability capabilities of RISs provide sufficient statistics to authenticate the legitimate transmitter at the physical layer.